From 3ba581201065248f5cff2de22aa972588258b246 Mon Sep 17 00:00:00 2001
From: Sebastian Fischer <sebf.fischer@gmail.com>
Date: Tue, 17 Oct 2023 10:36:58 +0200
Subject: [PATCH] Fix/duckdb missings (#34)

---
 DESCRIPTION                  | 2 +-
 NEWS.md                      | 4 ++++
 R/DataBackendDuckDB.R        | 2 +-
 tests/testthat/test_duckdb.R | 7 +++++++
 4 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/DESCRIPTION b/DESCRIPTION
index 0925a97..3b59d1a 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,6 +1,6 @@
 Package: mlr3db
 Title: Data Base Backend for 'mlr3'
-Version: 0.5.1
+Version: 0.5.1-9000
 Authors@R:
     person(given = "Michel",
            family = "Lang",
diff --git a/NEWS.md b/NEWS.md
index e46eb54..ad85f98 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,3 +1,7 @@
+# mlr3db 0.5.2
+
+- Bugfix: `DataBackendDuckDB` calculated missing values incorrectly
+
 # mlr3db 0.5.1
 
 - Compatibility with new duckdb version (#36).
diff --git a/R/DataBackendDuckDB.R b/R/DataBackendDuckDB.R
index 08da4c5..03d0dd3 100644
--- a/R/DataBackendDuckDB.R
+++ b/R/DataBackendDuckDB.R
@@ -188,7 +188,7 @@ DataBackendDuckDB = R6Class("DataBackendDuckDB", inherit = DataBackend, cloneabl
       )
 
       counts = unlist(DBI::dbGetQuery(private$.data, query), recursive = FALSE)
-      setNames(as.integer(self$nrow - counts), cols)
+      setNames(as.integer(length(rows) - counts), cols)
     }
   ),
 
diff --git a/tests/testthat/test_duckdb.R b/tests/testthat/test_duckdb.R
index 95ffe31..aa43425 100644
--- a/tests/testthat/test_duckdb.R
+++ b/tests/testthat/test_duckdb.R
@@ -62,3 +62,10 @@ test_that("multiple parquet file", {
   b = as_duckdb_backend(files)
   expect_backend(b)
 })
+
+test_that("missings are calculated correctly", {
+  d = data.frame(x = c(NA, 1), y = c(1, 1))
+  b = as_duckdb_backend(d, path = tempfile())
+  expect_equal(b$missings(1, "x"), c(x = 1))
+  expect_equal(b$missings(2, "x"), c(x = 0))
+})